Data storage devices such as disk drives are generally considered acceptable and usable even though they include one or more defective data storage locations. Such defective data storage locations, normally referred to as defective blocks, are usually identified during a disk format operation, wherein the defective blocks are identified and set aside not to be utilized, and an index or pointer is provided to the next good block of data storage locations.
A problem arises, however, when one or more data storage locations within a good block become defective after disk formatting. Most importantly, this problem will not manifest itself until a data read operation is attempted. At that time, the corrupt data is discovered, and generally, the uncorrupted data is irretrievably lost.